JUNEAU, Alaska (AP) — A team of aviation investigators is now working in a remote, mountainous site in southeast Alaska to determine what caused the crash of a sightseeing plane that killed eight cruise ship passengers and the aircraft’s pilot.

The turboprop floatplane went down Thursday. The excursion was sold through the cruise company Holland America.

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Seven investigators with the National Transportation Safety Board made it to the crash site on Saturday morning and are scouring for clues.

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An NTSB official says the plane was on its way back from the Misty Fjords National Monument, a wilderness area of lakes, snowcapped peaks and glacial valleys. The terrain where the plane crashed is steep, mountainous, and often sees strong winds and rain.

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The official says the airplane’s wings and tail broke off during impact, but the fuselage was largely intact. The plane crashed on a cliff, 800 feet above Ella Lake in steep, muddy terrain.